Method for recovering lithium from lithium ion battery scrap

ABSTRACT

A method for recovering lithium from lithium ion battery scrap according to this invention comprises subjecting lithium ion battery scrap to a calcination step, a crushing step, and a sieving step sequentially carried out, wherein the method comprises, between the calcination step and the crushing step, between the crushing step and the sieving step, or after the sieving step, a lithium dissolution step of bringing the lithium ion battery scrap into contact with water and dissolving lithium contained in the lithium ion battery scrap in the water to obtain a lithium-dissolved solution; a lithium concentration step of solvent-extracting lithium ions contained in the lithium-dissolved solution and stripping them to concentrate the lithium ions to obtain a lithium concentrate; and a carbonation step of carbonating the lithium ions in the lithium concentrate to obtain lithium carbonate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.16/499,173, filed on Sep. 27, 2019, which was filed as PCT InternationalApplication No. PCT/JP2018/013027 on Mar. 28, 2018, which claims thebenefit under 35 U.S.C. § 119(a) to Patent Application No. 2017-072018,filed in Japan on Mar. 31, 2017, all of which are hereby expresslyincorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a method for recovering lithium fromlithium ion battery scrap, and in particular, proposes a techniquecapable of effectively recovering lithium contained in lithium ionbattery scrap.

BACKGROUND ART

In recent years, it has been widely studied that valuable metals such asnickel and cobalt are recovered from lithium ion battery scrap and thelike discarded for expired product life or other reasons by means of wetprocessing or the like, in terms of effective utilization of resources.

For example, in order to recover valuable metals from lithium ionbattery scrap, the lithium ion battery scrap is typically calcined toremove harmful electrolytes and then subjected to crushing and sievingin this order. Subsequently, battery powder obtained under a sieve forthe sieving is leached by adding it to a leaching solution, wherebylithium, nickel, cobalt, manganese, iron, copper, aluminum and the likewhich can be contained therein are dissolved in the solution.

Then, iron, copper, aluminum, and the like are removed sequentially orsimultaneously among the respective metal elements dissolved in theleached solution to recover valuable metals such as cobalt, manganeseand nickel. More particularly, the leached solution is subjected tomultiple stages of solvent extraction or neutralization according to themetals to be separated, and further, each solution obtained at eachstage is subjected to stripping, electrolysis, carbonation or othertreatments. Accordingly, a lithium-containing solution containinglithium ions is obtained.

The lithium-containing solution thus obtained is generally subjected tocarbonation by adding a carbonate salt or blowing a carbon dioxide gasto recover a lithium ion contained in the lithium-containing solution aslithium carbonate.

As such a type of technique, Patent Document 1 discloses that a lithiumion is recovered as solid lithium carbonate by adjusting a pH of anaqueous solution containing lithium ions to pH 4 to 10 depending onacidic solvent extracting agent used for extraction of lithium ions,bringing the aqueous solution into contact with the acidic solventextracting agent to extract lithium ions, and then bringing the solventextracting agent into contact with an aqueous solution having a pH of3.0 or less to strip lithium ions, repeating the above strippingoperations using the resulting aqueous lithium ion solution toconcentrate the lithium ions, and mixing the resultinghigh-concentration lithium ion aqueous solution with a water-solublecarbonate while maintaining the high-concentration lithium ion aqueoussolution at 50° C. or higher.

CITATION LIST Patent Literature

Patent Document 1: Japanese Patent No. 4581553 B

SUMMARY OF INVENTION Technical Problem

However, the conventional method as described above recovers lithiumfrom the lithium-containing solution finally obtained through a largenumber of steps such as leaching and multistage solvent extraction, sothat the lithium-containing solution contains a significant amount ortype of impurities due to reagents and additives used in the largenumber of steps.

This will result in deteriorated quality of lithium carbonate obtainedby carbonation and causes a problem of increasing labors and costsrequired for purifying lithium carbonate to obtain high quality lithiumcarbonate.

This invention aims to solve such problems of the prior arts. An objectof the present invention is to provide a method for recovering lithium,which can effectively recover lithium that is contained in lithium ionbattery scrap.

Solution to Problem

The present inventors have focused on the fact that lithium contained inthe lithium ion battery scrap after the calcination step is easilydissolved in water, whereas other metals are in a form which isdifficult to dissolve in water. The present inventors have then foundthat the lithium ion battery scrap after the calcination step could bebrought into contact with water to obtain a lithium-dissolved solution,and then the lithium-dissolved solution could be subjected to solventextraction and stripping to increase a lithium ion concentrationeffectively.

Based on such findings, a method for recovering lithium from lithium ionbattery scrap according to this invention comprises subjecting lithiumion battery scrap to a calcination step, a crushing step, and a sievingstep sequentially carried out, wherein the method comprises, between thecalcination step and the crushing step, between the crushing step andthe sieving step, or after the sieving step, a lithium dissolution stepof bringing the lithium ion battery scrap into contact with water anddissolving lithium contained in the lithium ion battery scrap in thewater to obtain a lithium-dissolved solution; a lithium concentrationstep of solvent-extracting lithium ions contained in thelithium-dissolved solution and stripping them to concentrate the lithiumions to obtain a lithium concentrate; and a carbonation step ofcarbonating the lithium ions in the lithium concentrate to obtainlithium carbonate.

The lithium dissolution step is preferably carried out after the sievingstep.

In the lithium concentration step, the solvent extraction and thestripping are repeatedly carried out over a plurality of times.

For the solvent-extracting in the lithium concentration step, a solventextracting agent comprising 2-ethylhexyl 2-ethylhexylphosphonate ordi-2-ethylhexylphosphoric acid is preferably used.

A pH during the solvent-extracting in the lithium concentration step ispreferably from 5.0 to 6.5.

When the lithium concentrate obtained in the lithium concentration stepcontains nickel ions, the method for recovering lithium according tothis invention further comprises a neutralization step of neutralizingthe lithium concentrate to recover nickel before the carbonation step.

It is preferable that in the carbonation step, the carbonizing oflithium ions is carried out by adding a carbonate to or blowing a carbondioxide gas into the lithium concentrate, and a temperature of theconcentrate in the carbonating is 50° C. or higher.

Advantageous Effects of Invention

In the method for recovering lithium according to this invention, thelithium dissolution step is carried out between the calcination step andthe crushing step, between the crushing step and the sieving step, orafter the sieving step, and lithium ions in the lithium-dissolvedsolution thus obtained is concentrated by solvent extraction andstripping, whereby lithium carbonate with relatively high quality can beobtained in the carbonation step.

Therefore, according to method for recovering lithium according to thisinvention, lithium contained in the lithium ion battery scrap can beeffectively recovered.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart showing a lithium recovery method according to anembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail.

In the method for recovering lithium according to one embodiment of thepresent invention, when carrying out a calcination step, a crushingstep, and a sieving step in this order on the lithium ion battery scrap,a lithium dissolution step is carried out between the calcination stepand the crushing step (immediately after the calcination), between thecrushing step and the sieving step (immediately after carrying out thecalcination and crushing in this order), or after the sieving step(immediately after carrying out the calcination, crushing and sieving inthis order), and after the lithium dissolution step, a lithiumconcentration step and a carbonation step are sequentially carried out,as illustrated in FIG. 1 .

Here, in the lithium dissolution step, lithium contained in the lithiumion battery scrap is dissolved in water to obtain a lithium-dissolvedsolution. The lithium concentration step is a step of obtaining alithium concentrate in which lithium ions are concentrated by solventextraction and stripping of lithium ions contained in thelithium-dissolved solution. Further, the carbonation step is a step ofcarbonating the lithium ions in the concentrate to obtain lithiumcarbonate.

(Lithium Ion Battery Scrap)

Lithium ion battery scrap targeted by this invention is lithium ionbatteries that can be used in mobile phones and other various electronicdevices and have been discarded due to expired battery product life,production defects or other reasons. It is preferable to recover lithiumfrom such lithium ion battery scrap in terms of effective utilization ofresources.

Here, this invention is directed to lithium ion battery scrap containingat least lithium. In an embodiment of this invention, the lithium ionbattery scrap generally contains from 0.1% to 10% by mass of lithium.

In general, the lithium ion battery scrap has a housing containingaluminum as an exterior that wraps around the lithium ion battery scrap.Examples of the housing include those made only of aluminum and thosecontaining aluminum, iron, aluminum laminate, and the like.

The lithium ion battery scrap may also contain, in the above housing,positive electrode active materials composed of one or more single metaloxides or two or more composite metal oxides or the like, of ithium,nickel, cobalt and manganese, and aluminum foils (positive electrodesubstrate) to which the positive electrode active materials are appliedand fixed by, for example, polyvinylidene fluoride (PVDF) or otherorganic binder. In addition, the lithium ion battery may contain copper,iron, or the like.

Further, the lithium ion battery scrap generally contains electrolyticsolutions in the housing. For example, ethylene carbonate, diethylcarbonate or the like may be used as the electrolytic solution.

(Calcination Step)

In the calcination step, the lithium ion battery scrap is heated. Thecalcination step is generally carried out for the purposes of increasinga temperature of the lithium ion battery scrap, removing the internalelectrolytic solutions to renders them harmless, and also decomposingthe binder that binds the aluminum foils to the positive electrodeactive materials to facilitate separation of the aluminum foils from thepositive electrode active materials during crushing and sieving andincrease a recovery rate of the positive electrode active materialsrecovered under the sieve, and further changing a metal such as cobaltcontained in the lithium ion battery scrap to a form of the metal whichcan be easily dissolved in the leaching with an acid, and the like.

Through the calcination step, lithium in the lithium ion battery scrapwill be in the form of lithium oxide or lithium carbonate or the like,and this form of lithium is easily dissolved in water. On the otherhand, metals such as cobalt are difficult to be dissolved in water. Byutilizing such a difference of solubility in water of the metalscontained in the lithium ion battery scrap after the calcination step tocarried out a lithium dissolving step as described below, only lithiumin the lithium ion battery scrap can be selectively removed to recoverlithium at an early stage in processing of the lithium ion batteryscrap. As a result, it is possible to prevent substances contained invarious reagents that can be used in the processing of lithium ionbattery scrap from being mixed into lithium carbonate finally obtained,whereby high quality lithium carbonate is produced.

From such a viewpoint, in the calcination step, the lithium ion batteryscrap is preferably heated by maintaining it in a temperature range offrom 550° C. to 650° C. for 1 hour to 4 hours. If the heatingtemperature is too low or the heating time is too short, the change oflithium to a form that is easily dissolved in water would beinsufficient, and there is a concern that a large amount of lithiumcannot be dissolved in the lithium dissolution step. On the other hand,if the heating temperature is too high or the heating time is too long,aluminum deteriorates to become powdered during crushing, and there is arisk that a large number of aluminum will be mixed in the sievedproduct. In addition, the above temperature is measurable by measuring asurface temperature of the housing of the lithium ion battery scrap.

The calcination step can be carried out by using various heatingequipment such as a rotary kiln furnace or other various furnaces, and afurnace for heating in an air atmosphere, as long as the temperature ofthe lithium ion battery scrap can be controlled as described above.

(Crushing Step)

In this embodiment, after heating the lithium ion battery scrap in thecalcination step, a crushing step of removing positive electrodematerials and negative electrode materials from the housing is carriedout.

In other embodiments, the lithium ion battery scrap after thecalcination step can be subjected to a lithium dissolution step asdescribed below. In this case, residues that remain undissolved in thelithium dissolution step can be subjected to the crushing step and asubsequent sieving step.

The crushing step is carried out to selectively separate the positiveelectrode active materials from the aluminum foils to which the positiveelectrode active materials are applied, while destroying the housing ofthe lithium ion battery scrap.

Various known apparatuses or devices can be used herein. In particular,it is preferable to use an impact-type crusher that can crush lithiumion battery scrap by applying an impact while cutting. Examples of theimpact-type crusher include a sample mill, a hammer mill, a pin mill, awing mill, a tornado mill, and a hammer crusher. It should be noted thata screen can be installed at an exit of the crusher, whereby the lithiumion battery scrap is discharged from the crusher through the screen whencrushed to a size that can pass through the screen.

(Sieving Step)

In this embodiment, after crushing the lithium ion battery scrap in thecrushing step, the lithium ion battery scrap is sieved using a sievehaving an appropriate opening, for example, for the purpose of removingaluminum powder. Thus, for example, aluminum or copper remains on thesieve, and powdered lithium ion battery scrap from which aluminum orcopper has been removed to some extent can be obtained below the sieve.

However, in other embodiments, after the crushing step, the lithiumdissolution step as described later for dissolving lithium in thelithium ion battery scrap can be carried out, and in this case, residuesremaining undissolved in the lithium dissolution step can be subjectedto the sieving step.

(Lithium Dissolution Step)

After the calcination step, after the crushing step or after the sievingstep, the lithium ion battery scrap is brought into contact with waterin the lithium dissolving step to dissolve lithium contained in thelithium ion battery scrap in the water. This can provide alithium-dissolved solution containing lithium ions.

In view of handling, the lithium dissolution step is preferably carriedout after all of the calcination step, the crushing step, and thesieving step. For example, when the lithium dissolution step is carriedout before the crushing step or before the sieving step, it is necessaryto dry residues after lithium dissolution.

In the lithium dissolution step, as described above, lithium in thelithium ion battery scrap that has undergone the calcination step isdissolved in water, but other metals are hardly dissolved. Therefore,the lithium contained in the lithium ion battery scrap can beeffectively separated herein.

Specifically, the water brought into contact with the lithium ionbattery scrap is tap water, industrial water, distilled water, purifiedwater, ion exchange water, pure water, ultrapure water, or the like.

The lithium-dissolved solution obtained after dissolving lithium has ahigh pH due to the dissolution of lithium. Therefore, an acid such assulfuric acid may be added to the above water so that a pH of thelithium-dissolved solution is from 7 to 10. The acid may be added at anyperiod before, during and/or after the dissolution of lithium. The pH ofthe lithium-dissolved solution finally obtained is preferably from 7 to10.

The reason is that if the pH of the lithium-dissolved solution is lessthan 7, metals such as Co may begin to dissolve, and if it is more than10, aluminum may begin to dissolve.

A method for bringing the lithium ion battery scrap into contact withthe water includes various methods such as spraying, immersing, dipping,and the like. In terms of reaction efficiency, a method for immersingand stirring the lithium ion battery scrap in water is preferable.

A temperature of the solution during the contact of the lithium ionbattery scrap with water can be from 10° C. to 60° C. A pulpconcentration can be from 50 g/L to 150 g/L. The pulp concentrationmeans a ratio of dry weight (g) of the lithium ion battery scrap to anamount of water (L) that is brought into contact with the lithium ionbattery scrap.

In the lithium dissolution step, a leaching rate of lithium in water ispreferably from 30% to 70%, and more preferably from 45% to 55%.

The lithium concentration of the lithium-dissolved solution ispreferably from 1.0 g/L to 3.0 g/L, and more preferably from 1.5 g/L to2.5 g/L. The lithium-dissolved solution may contain from 0 mg/L to 1000mg/L of sodium and from 0 mg/L to 500 mg/L of aluminum.

Residues that remain without being dissolved in water, among the lithiumion battery scrap, are removed by solid-liquid separation, and they canbe then subjected to acid leaching, solvent extraction, electrowinningor other treatments using known methods to recover various metalscontained therein. Here, detailed descriptions of the residues areomitted.

(Lithium Concentration Step)

The lithium-dissolved solution obtained in the lithium dissolving stepcontains lithium ions at a relatively low concentration. In order toconcentrate the lithium ions in the lithium-dissolved solution, alithium concentration step is carried out by solvent extraction andstripping (back extraction).

A solvent extracting agent used herein preferably includes 2-ethylhexyl2-ethyl hexylphosphonate or di-2-ethylhexylphosphoric acid.

When the solvent extraction is carried out using such a solventextracting agent, lithium is extracted from the lithium-dissolvedsolution (an aqueous phase) to the solvent extracting agent (an organicphase), and the organic phase is subjected to stripping. When theextraction and stripping are repeated over a plurality of times, thelithium concentration in the stripped solution increases, and finallylithium ions can be concentrated. This can provide a lithium concentratecontaining a high concentration of lithium ions.

A pH during the solvent extraction is preferably from 5.0 to 6.5. If thepH is less than 5.0, Li may be stripped. If the pH is more than 6.5, theexcessive high pH will result in poor phase separation, which may causea risk of a step trouble.

A lithium concentration of the lithium concentrate is preferably from5.0 g/L to 30.0 g/L, and more preferably from 10.0 g/L to 20.0 g/L.

(Neutralization Step)

The lithium concentrate may contain nickel ions derived from the lithiumion battery scrap or the like, for example in an amount of from 50 g/Lto 150 g/L. In this case, a neutralization step can be carried out toseparate and recover nickel from the lithium concentrate.

On the other hand, the neutralization step may be omitted when nickel isnot contained in the lithium concentrate or when it is contained in aminor amount.

In the neutralization step, the lithium concentrate is neutralized byadding a calcium salt, a sodium salt, or the like to the lithiumconcentrate, thereby precipitating the nickel ions in the lithiumconcentrate as a solid, which is separated by solid-liquid separation.

Examples of the calcium salt include calcium hydroxide, calcium oxide,and calcium carbonate. Examples of the sodium salt include sodiumhydroxide. However, a type of the additive is not particularly limitedas long as the additive can be increased to a desired pH.

A pH of the lithium concentrate before neutralization is, for example,from about −1 to 2. However, the pH of the lithium concentrate afterneutralization is preferably 9 or more, particularly from 9 to 13 byadding the above calcium salt or the like. If the pH afterneutralization is too low, it will result in insufficient nickelseparation, which may cause a deterioration of the quality of lithiumcarbonate. On the other hand, if the pH after neutralization is toohigh, an amphoteric metal may be re-dissolved if the solution containsthe amphoteric metal as an impurity.

In addition, after adding the calcium salt or the like to the lithiumconcentrate, the lithium concentrate can be stirred over a certainperiod of time to accelerate the reaction. In terms of improving thereaction efficiency, it is preferable that the temperature is relativelyhigh and the stirring is relatively strong.

After nickel is precipitated as a given compound such as a hydroxide byaddition of the calcium salt, or the like, nickel can be separated bysolid-liquid separation using a known apparatus or method such as afilter press or thickener.

A nickel concentration in the neutralized solution is preferably 5 mg/Lor less, particularly preferably 1 mg/L or less.

(Lithium Carbonation Step)

After the lithium concentration step or the neutralization step, thelithium concentrate is subjected to a lithium carbonation step torecover lithium contained in the lithium concentrate. Here, the lithiumions in the lithium concentrate are recovered as lithium carbonate byadding a carbonate to or blowing a carbon dioxide gas into the lithiumconcentrate.

After adding the carbonate or blowing the carbon dioxide gas, theconcentrate is maintained at a temperature preferably in a range of from50° C. to 90° C. for a certain period of time, with optionally stirring.

Examples of the carbonate added to the solution after neutralizationinclude sodium carbonate.

An amount of the carbonate added can be, for example, 1.0 to 2.0 foldmolar equivalent, preferably from 1.0 to 1.2 fold molar equivalent.

When the quality of lithium of the lithium carbonate thus obtained islower than a target quality, the lithium carbonate can be purified asneeded to obtain high quality lithium carbonate. Here, the targetlithium quality of lithium carbonate can be, for example, 16% or more,and preferably 17% or more.

More particularly, the lithium carbonate is purified by subjecting thelithium carbonate obtained by adding the carbonate to the lithiumconcentrate to re-pulp washing, and also blowing carbon dioxide there todissolve carbonic acid in the solution, and then separating a lithiumhydrogen carbonate solution from calcium, magnesium and the like bysolid-liquid separation. Subsequently, after deoxidizing andconcentrating, purified lithium carbonate is separated from a filtrateby solid-liquid separation. If the impurity quality in the purifiedlithium carbonate is high, further washing can be carried out.

EXAMPLES

Next, the method for recovering lithium according to this invention wasexperimentally carried out and the effects thereof were confirmed, asdescribed below. However, the descriptions herein are merely forillustrative and are not intended to be limited.

The calcination step, the crushing step and the sieving step werecarried out in this order, and two types of lithium ion battery scrap Aand B as shown in Table 1 under the sieve (<1 mm) were mixed, and themixture was added to water at a pulp concentration of 117 g/L. Themixture was stirred for 1 hour at a solution temperature d of 10° C. andthen allowed to stand for 2 hours to obtain a lithium-dissolvedsolution. The results are shown in Table 2.

The water was used in which 3% sulfuric acid was added to 1 fold molarequivalent of Mn to Zn in the lithium ion battery scrap.

Wet Moisture Dry Weight Content Weight (kg) (%) (kg) Mn Co Ni Li Fe AlCu Zn Scrap A 273.5 1 271.6 1.0 32.3 6.8 4.3 0.3 8.4 2.5 0.0 Scrap B254.0 0 253.4 1.2 25.8 3.5 3.8 0.3 5.5 2.8 0.0

TABLE 2 Li Na Al Leaching Rate (%) 54 — 0 Leaching Concentration (g/L)2.5 0.037 0.022

In view of the foregoing, it was found that lithium in the lithium ionbattery scrap could be effectively dissolved in water, and thelithium-dissolved solution contained substantially no sodium or thelike.

1. A method for recovering lithium from lithium ion battery scrap whichhas been subjected to a calcination step performed in a temperaturerange of from 550° C. to 650° C., the method comprising: a lithiumdissolution step of bringing the lithium ion battery scrap into contactwith water and dissolving lithium contained in the lithium ion batteryscrap in the water to obtain a lithium-dissolved solution, wherein thelithium-dissolved solution is from 7 to
 10. 2. The method according toclaim 1, wherein the method further comprises a lithium concentrationstep of concentrating the lithium in the lithium-dissolved solution toobtain a lithium concentrate.
 3. The method according to claim 2,wherein the method further comprises a carbonation step of carbonatingthe lithium in the lithium concentrate to obtain lithium carbonate. 4.The method according to claim 1, wherein an aluminum concentration ofthe lithium-dissolved solution is from 0 mg/L to 500 mg/L.
 5. The methodaccording to claim 2, wherein the lithium concentrate obtained in thelithium concentration step contains nickel ions, wherein the methodfurther comprises a neutralization step of neutralizing the lithiumconcentrate to recover nickel before the carbonation step.
 6. The methodaccording to claim 3, wherein in the carbonation step, the carbonizingof lithium ions is carried out by adding a carbonate to or blowing acarbon dioxide gas into the lithium concentrate, and a temperature ofthe concentrate in the carbonating is 50° C. or higher.
 7. The methodaccording to claim 1, further comprising subjecting the lithium ionbattery scrap to a calcination step to a crushing step, and a sievingstep.
 8. The method according to claim 7, wherein the crushing step andthe sieving step are performed in this order, and wherein the lithiumdissolution step is performed before the crushing step, between thecrushing step and the sieving step, or after the sieving step.
 9. Themethod according to claim 8, wherein the lithium dissolution step iscarried out after the sieving step.
 10. The method according to claim 1,wherein the lithium ion battery scrap which has been subjected to acalcination step contains lithium oxide or lithium carbonate.
 11. Themethod according to claim 1, wherein in the lithium dissolution step, anacid is added to the water so that the pH of the lithium-dissolvedsolution is from 7 to
 10. 12. The method according to claim 1, whereinin the lithium dissolution step, a leaching rate of lithium in water isfrom 30% to 70%.
 13. The method according to claim 1, wherein in thelithium dissolution step, a leaching rate of lithium in water is from45% to 55%.
 14. The method according to claim 1, wherein lithiumconcentration of the lithium-dissolved solution is from 1.0 g/L to 3.0g/L.
 15. The method according to claim 1, wherein lithium concentrationof the lithium-dissolved solution is from 1.5 g/L to 2.5 g/L.